<PAGE>

                                                                    EXHIBIT 10.5

IRREVOCABLE STANDBY LETTER OF CREDIT NO. SVBSF002458

DATE: SEPTEMBER 18, 2003

BENEFICIARY:
CA-OAKBROOK PLAZA LAGUNA LIMITED PARTNERSHIP,
2 North Riverside Plaza, Suite 2100
Chicago, IL 60606

APPLICANT:
INTERCHANGE CORPORATION
Attention: Doug Norman
24422 Avenida de la Carlota
Suite 120
Laguna Hills, CA 92653

AMOUNT: US$80,000.00 (U.S. DOLLARS EIGHTY THOUSAND EXACTLY)

EXPIRATION DATE: SEPTEMBER 18, 2004

LOCATION: SANTA CLARA, CALIFORNIA

DEAR SIR/MADAM:

WE HEREBY ESTABLISH OUR IRREVOCABLE STANDBY LETTER OF CREDIT NO. SVBSF______ IN
YOUR FAVOR AVAILABLE BY YOUR DRAFTS DRAWN ON US AT SIGHT IN THE FORM OF "EXHIBIT
B" ATTACHED AND ACCOMPANIED BY THE FOLLOWING DOCUMENTS:

1.    THE ORIGINAL OF THIS LETTER OF CREDIT AND ALL AMENDMENT(S), IF ANY.

2.    SIGHT DRAFTS DRAWN ON US.

3.    A DATED CERTIFICATION FROM THE BENEFICIARY SIGNED BY AN AUTHORIZED
      OFFICER, FOLLOWED BY ITS DESIGNATED TITLE, STATING THE FOLLOWING:

      (A)   "AN EVENT OF DEFAULT (AS DEFINED IN THE LEASE) HAS OCCURRED BY
            INTERCHANGE CORPORATION AS TENANT UNDER THAT CERTAIN LEASE AGREEMENT
            BETWEEN TENANT, AND EOP-OAKBROOK PLAZA LAGUNA, L.L.C., a DELAWARE
            LIMITED LIABILITY COMPANY AS LANDLORD. FURTHERMORE THIS IS TO
            CERTIFY THAT: (I) LANDLORD HAS GIVEN WRITTEN NOTICE TO TENANT TO
            CURE THE DEFAULT PURSUANT TO THE TERMS OF THE LEASE; (II) SUCH
            DEFAULT HAS NOT BEEN CURED UP TO THIS DATE OF DRAWING UNDER THIS
            LETTER OF CREDIT; AND (III) LANDLORD IS AUTHORIZED TO DRAW DOWN ON
            THE LETTER OF CREDIT. AND

      (B)   THIS IS TO CERTIFY THAT LANDLORD WILL HOLD THE FUNDS DRAWN UNDER
            THIS LETTER OF CREDIT AS SECURITY DEPOSIT FOR TENANT OR APPLY SAID
            FUNDS TO TENANT'S OBLIGATION UNDER THE LEASE."

      PARTIAL DRAWS ARE ALLOWED. THIS ORIGINAL LETTER OF CREDIT MUST ACCOMPANY
      ANY DRAWINGS HEREUNDER FOR ENDORSEMENT OF THE DRAWING AMOUNT AND WILL BE
      RETURNED TO THE BENEFICIARY UNLESS IT IS FULLY UTILIZED.

                                   PAGE 1 OF 2
<PAGE>

IRREVOCABLE STANDBY LETTER OF CREDIT NO. SVBSF002458
DATED SEPTEMBER 18, 2003

THIS LETTER OF CREDIT SHALL AUTOMATICALLY REDUCE IN ACCORDANCE WITH THE
FOLLOWING SCHEDULE:

<TABLE>
<CAPTION>
                             NEW REDUCED AMOUNT
EFFECTIVE DATE               OF LETTER OF CREDIT
<S>                          <C>
APRIL 1, 2004                     $64,000
APRIL 1, 2005                     $51,200
APRIL 1, 2006                     $40,960
</TABLE>

THIS LETTER OF CREDIT SHALL BE AUTOMATICALLY EXTENDED FOR AN ADDITIONAL PERIOD
OF ONE YEAR, WITHOUT AMENDMENT, FROM THE PRESENT OR EACH FUTURE EXPIRATION DATE
UNLESS AT LEAST 60 DAYS PRIOR TO THE THEN CURRENT EXPIRATION DATE WE NOTIFY YOU
BY REGISTERED MAIL/OVERNIGHT COURIER SERVICE AT THE ABOVE ADDRESS THAT THIS
LETTER OF CREDIT WILL NOT BE EXTENDED BEYOND THE CURRENT EXPIRATION DATE. IN NO
EVENT SHALL THIS LETTER OF CREDIT BE AUTOMATICALLY EXTENDED BEYOND APRIL 1,
2007.

THIS LETTER OF CREDIT MAY ONLY BE TRANSFERRED IN ITS ENTIRETY BY THE ISSUING
BANK, ASSUMING SUCH TRANSFER TO SUCH TRANSFEREE WOULD BE IN COMPLIANCE WITH THEN
APPLICABLE LAW AND REGULATIONS, INCLUDING BUT NOT LIMITED TO THE REGULATIONS OF
THE U.S. DEPARTMENT OF TREASURY AND U.S. DEPARTMENT OF COMMERCE, UPON OUR
RECEIPT OF THE ATTACHED "EXHIBIT A" DULY COMPLETED AND EXECUTED BY THE
BENEFICIARY AND ACCOMPANIED BY THE ORIGINAL LETTER OF CREDIT AND ALL
AMENDMENT(S), IF ANY, TOGETHER WITH THE PAYMENT OF OUR TRANSFER FEE 1/4 OF 1% OF
THE TRANSFER AMOUNT (MINIMUM USD250.00).

DRAFT(S) AND DOCUMENTS MUST INDICATE THE NUMBER AND DATE OF THIS LETTER OF
CREDIT.

DOCUMENTS MUST BE FORWARDED TO US BY OVERNIGHT DELIVERY SERVICE TO: SILICON
VALLEY BANK, 3003 TASMAN DRIVE, SANTA CLARA CA 95054, ATTN: INTERNATIONAL
DIVISION.

WE HEREBY AGREE WITH THE DRAWERS, ENDORSERS AND BONAFIDE HOLDERS THAT THE DRAFTS
DRAWN UNDER AND IN ACCORDANCE WITH THE TERMS AND CONDITIONS OF THIS LETTER OF
CREDIT SHALL BE DULY HONORED UPON PRESENTATION TO THE DRAWEE, IF NEGOTIATED ON
OR BEFORE THE EXPIRATION DATE OF THIS CREDIT.

THIS LETTER OF CREDIT IS SUBJECT TO THE UNIFORM CUSTOMS AND PRACTICE FOR
DOCUMENTARY CREDITS (1993 REVISION), INTERNATIONAL CHAMBER OF COMMERCE,
PUBLICATION NO. 500.

     /s/ John S. Dossantos                     /s/ Alice E. Deluz
  ---------------------------              ---------------------------
     AUHORIZED SIGNATURE                      AUTHORIZED SIGNATURE

                                   PAGE 2 OF 2
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                                   EXHIBIT "A"

DATE:

TO: SILICON VALLEY BANK
    3003 TASMAN DRIVE                     RE: STANDBY LETTER OF CREDIT
    SANTA CLARA, CA 95054                      NO.                   ISSUED BY
    ATTN:INTERNATIONAL DIVISION.               SILICON VALLEY BANK, SANTA CLARA
       STANDBY LETTERS OF CREDIT               L/C AMOUNT:

GENTLEMEN:

FOR VALUE RECEIVED, THE UNDERSIGNED BENEFICIARY HEREBY IRREVOCABLY TRANSFERS TO:

(NAME OF TRANSFEREE)
(ADDRESS)

ALL RIGHTS OF THE UNDERSIGNED BENEFICIARY TO DRAW UNDER THE ABOVE LETTER OF
CREDIT UP TO ITS AVAILABLE AMOUNT AS SHOWN ABOVE AS OF THE DATE OF THIS
TRANSFER.

BY THIS TRANSFER, ALL RIGHTS OF THE UNDERSIGNED BENEFICIARY IN SUCH LETTER OF
CREDIT ARE TRANSFERRED TO THE TRANSFEREE. TRANSFEREE SHALL HAVE THE SOLE RIGHTS
AS BENEFICIARY THEREOF, INCLUDING SOLE RIGHTS RELATING TO ANY AMENDMENTS,
WHETHER INCREASES OR EXTENSIONS OR OTHER AMENDMENTS, AND WHETHER NOW EXISTING OR
HEREAFTER MADE. ALL AMENDMENTS ARE TO BE ADVISED DIRECT TO THE TRANSFEREE
WITHOUT NECESSITY OF ANY CONSENT OF OR NOTICE TO THE UNDERSIGNED BENEFICIARY.

THE ORIGINAL OF SUCH LETTER OF CREDIT IS RETURNED HEREWITH, AND WE ASK YOU TO
ENDORSE THE TRANSFER ON THE REVERSE THEREOF, AND FORWARD IT DIRECTLY TO THE
TRANSFEREE WITH YOUR CUSTOMARY NOTICE OF TRANSFER.

SINCERELY,

_____________________________
     (BENEFICIARY'S NAME)

_____________________________
 SIGNATURE OF BENEFICIARY

SIGNATURE AUTHENTICATED

_____________________________
    (NAME OF BANK)

_____________________________
   AUTHORIZED SIGNATURE

<PAGE>

                                   EXHIBIT "B"

     DATE: _______________                         REF. NO. ___________________

     AT SIGHT OF THIS DRAFT

     PAY TO THE ORDER OF   ____________________________  US$___________________

     USDOLLARS ________________________________________________________________
     __________________________________________________________________________

     DRAWN UNDER SILICON VALLEY BANK, SANTA CLARA, CALIFORNIA, STANDBY
     LETTER OF CREDIT NUMBER NO. ____________________ DATED ___________________

     TO: SILICON VALLEY BANK
         3003 TASMAN DRIVE                      _______________________________
         SANTA CLARA, CA 95054                     (BENEFICIARY'S NAME)

                                                _______________________________
                                                   AUTHORIZED SIGNATURE

                         GUIDELINES TO PREPARE THE DRAFT

1.    DATE: ISSUANCE DATE OF DRAFT.

2.    REF. NO.: BENEFICIARY'S REFERENCE NUMBER, IF ANY.

3.    PAY TO THE ORDER OF: NAME OF BENEFICIARY AS INDICATED IN THE L/C (MAKE
      SURE BENEFICIARY ENDORSES IT ON THE REVERSE SIDE).

4.    US$: AMOUNT OF DRAWING IN FIGURES.

5.    USDOLLARS: AMOUNT OF DRAWING IN WORDS.

6.    LETTER OF CREDIT NUMBER: SILICON VALLEY BANK'S STANDBY L/C NUMBER THAT
      PERTAINS TO THE DRAWING.

7.    DATED: ISSUANCE DATE OF THE STANDBY L/C.

8.    BENEFICIARY'S NAME: NAME OF BENEFICIARY AS INDICATED IN THE L/C.

9.    AUTHORIZED SIGNATURE: SIGNED BY AN AUTHORIZED SIGNER OF BENEFICIARY.

IF YOU NEED FURTHER ASSISTANCE IN COMPLETING THIS DRAFT, PLEASE CALL OUR L/C
PAYMENT SECTION AND ASK FOR:

ALICA DA LUZ: 408-654-7120